Antenna positioning systems typically point an antenna towards a satellite in geosynchronous orbit above the earth to acquire the signals emitted from the transponder of the satellite. Antenna positioning systems typically include, inter alia, a dish or reflector and a feed or feed horn. The reflector receives the signals broadcast from the satellite transponder and focuses them on a focal point where the feed is located.
Some antenna reflectors focus the signals on a focal point located at the center axis of the reflector. Other antenna reflectors focus the signals on a focal point which is offset from the center axis of the reflector. The purpose of the offset design is to move the antenna feed out of the path of the incoming signal from the satellite to reduce the shadowing found in satellite systems with center axis feeds.
Some satellites may transmit signals in a circular band or in a linear polarization plane. In order to acquire signals transmitted in the linear polarization plane, the skew angle, or skew offset, of the reflector must be adjusted.
Some conventional antenna positioning systems with a centrally located focal point and feed rely on manually rotating the antenna to adjust the skew angle. Conventional antenna positioning systems with an offset focal point and offset feed similarly rotate the reflector and feed about the offset axis to adjust the skew angle. Such offset positioning systems may include features to automatically adjust the skew angle. However, the offset antenna positioning systems may require various components associated with transmitting and receiving signals to be located in or on the offset feed. The offset feed also requires a longer RF path which will induce losses. The offset design also results in a larger moment arm and therefore requires a larger and more powerful drive motor to rotate the antenna reflector.
Commercial and military satellites have both beacon and transponder broadcasts. Each satellite typically has multiple transponders that are used for data transfer. These transponders often have overlapping areas of reception on the surface of the earth. Users of satellite antenna systems need to orient the receiving antenna dish to the correct azimuth and elevation to receive an optimal signal from the desired satellite. For satellite signals broadcast in a linear polarization plane, the correct skew angle must also be set. Users need to differentiate between the desired signal from all other signals that can be received at a single location.
Conventional satellite antenna systems, for acquiring broadcast transponder signals from a satellite, may use the GPS location of the satellite antenna, the coordinates of the satellite, and a compass to orient the receiver dish to the correct azimuth. An inclinometer may be used to orient the reflector or dish to the correct elevation, and a skew adjustment is done manually or automatically by inputting the values from a preset table of values for a particular satellite and transponder. Such steps may have inherent errors due to the mechanical placement of the various components.
After the antenna dish is pointed to the desired satellite, conventional systems rely on a terminal and software to identify the received signals. Using the manually input information, the user identifies multiple signals, each of varying strength, which the terminal is receiving. Software may then be used to identify which of the broadcasted transponder signals the antenna positioning system is receiving and the result may be displayed on a terminal. If the signal strength is inadequate, the user must manually adjust the antenna orientation to maximize the signal. This alignment can be performed either by mechanical adjustments or motorized adjustments via a terminal application. The antenna is moved again until the data appears to be consistently streamed via the software application. However, such a technique requires significant user analysis and intervention. The manual acquisition of the satellite signal is also cumbersome, time consuming and inefficient. The existing process also relies on a single, fixed satellite configuration, however satellite configurations may change.
Conventional antenna positioning systems also typically include a modem to form a signal lock after the operator has positioned the antenna to maximize the energy per bit of signal. However, using a modem may require additional components, complexity, and expense to the antenna positioning system. Also, a modem provisioned for one satellite broadcast signal may not operate correctly for other satellite broadcast signals. Other conventional antenna positioning systems may rely on a reference satellite to calculate the position of the desired satellite. However, the configuration of the reference satellite may change resulting in the need to recalibrate the system.